The Genus Houlletia

Brongniart

The genus Houlletia was established by French botanist Adolphe Théodore (de) Brongniart (1801-1876), who published Houlletia stapeliaeflora (now Houlletia brocklehurstiana in 1841. The genus is named in honor of a French orchid collector in Brazil, M. Houllet, who later became director of the Botanic Jardin des Plantes in Paris. The genus is abbreviated "Hlt."
Photo above, left, taken in Parque Nacional da Tijuca near Rio in March 2008, by Phil Whittman (www.canopyaccess.com).

These are large-growing orchids with 20-25 species, known from Mexico (or possibly Guatemala) through Central and South America, east to the Brazilian Atlantic highlands and south to Bolivia. They are found growing epiphytically and terrestrially on embankments in cool, humid, wet areas, 1,000-2,200 m elevation.

The plants have ovoid, ridged pseudobulbs, each bearing 1-2 large, pleated leaves.
The inflorescences begin from the base of the pseudobulbs and are arching or pendant, with fleshy, showy flowers on a simple raceme. The dorsal sepal is free and the lateral sepals form a short mentum with the column foot. The petals are similar to the dorsal sepal. The lip is deeply 3-lobed, the lateral lobes are upcurved and the midlobe is wide and triangular. The anther contains two waxy pollinia. Dressler (1993a) has a line-drawing of a presumably similar Lacaena pollinarium.

Culture:

Christo Page, Glenstantia, South Africa (January 2001), wrote:
"The plant was [grown] in a rockwool/polystyrene mixture in a basket... Temperature is controlled between 13ºC and about 28ºC and humidity stays above about 50% throughout. The plant is watered once a week in summer and once in 10 days during the winter. It gets fertilized with every watering. Once a month clean water is used to flush the growing medium.
"Fairly soon after the magnificent display of flowers which led to it being judged, the plant rapidly declined in health. This necessitated drastic measures of cleaning it from old rotten pseudobulbs and repotting it in a more porous growth medium of about 60% milled polystyrene, 10% perlite and 30% milled rockwool.
"It, therefore, seems as if it is essential to grow Houlletias in a very porous medium or epiphytically while maintaining high humidity in the atmosphere, good air movement and no temperature extremes. A slightly drier regime in winter may also be advantageous. Good quality water is also necessary for soft leaved orchids as they quite easily show chemical leaf burn."

Rand (1876), wrote:
"These plants should be grown in well-drained pots, in peat, and need plenty of moisture and frequent watering when in full growth. During the resting season they should be kept in the cold house, nearly dry. The genus seems to be neglected by orchid growers, but for no good reason. All the species are of easy culture, bloom freely, and are very handsome."

Taxonomy:
Gerlach (1999) places the genus Houlletia within the "Acineta-Verwandtschaftsgruppe," allied with Acineta, Lueddemannia, and Vasqueziella within the larger Stanhopinae Alliance.

Whitten, Williams, and Chase distinguish the Houlletia clade among the Stanhopinae, comprising Horichia, Houlletia, Paphinia, Schlimmia, and Trevoria. They write: "As presently defined, Houlletia consists of two morphologically distinct groups. The ["Euhoulletia" of Schlechter] group containing Hlt. brockelhurstiana (the type species), Hlt. tigrina, Hlt. odoratissima Linden ex Lindl., and Hlt. juruenensis Hoehne have open, resupinate flowers that are heavily spotted in red-brown. The epichile is triangular and the hypochile bears a pair of curved, acute projections; the lip shares many features of the lip of Paphinia. The viscidium is narrow, approximately the same width of the long stipe, and the pollinaria are deposited on the bee's scutellum.

In contrast, the ["Neohoulletia" of Schlechter] group containing Hlt. sanderi, Hlt. wallisii, Hlt. clarae Schltr., and Hlt. lowiana Rchb.f. has globose, nonresupinate flowers that are white to yellow, mostly unspotted, and borne on an erect inflorescence. The epichile is rectangular or ovate (not triangular), and the lateral projections on the hypochile are broad instead of acute. The pollinarium has a broad, concave viscidium."

I was lucky enough to have seen hundreds of these plants growing in Tijuca National Park in the hills just inland of Rio de Janeiro, March 2008. Several plants were in bloom, although almost every flower had been chewed by hungry denizens of the forest floor (photo of still-intact buds at right).

Houlletia brocklehurstiana 'Imperial Topaz' AM/SAOC (South African Orchid Council), awarded in March 1997 (ratified October 1999 and chosen as plant of the year by the SAOC).
Awarded to Christo and Aletta Page, Glenstantia, RSA.
Inflorescence was 36.5 cm long, with seven large, fleshy flowers. Horizontal natural spread 8 cm. Flowers are white, creamy brown, and red brown, and the base color of the sepals and petals appears rich topaz.
Photo.

* Houlletia sanderi Rolfe 1910 - now Jennyella sanderi [Ecuador]
Photo at right by Ecuagenera. Species was also known as Hlt. elata. Note that lip structure differs greatly from the red spotted species; the epichile is not triangular. In 1999, Luckel & Fessel moved this species into the new genus, Jennyella, named for Swiss botanist and taxonomist Rudolf Jenny.

This secies has earned two HCC/AOS awards under the name Hlt. tigrina and a CHM/AOS under the synonym Hlt. landsbergii. See lithograph at right - this was published as Hlt. landsbergii. Lithograph below, as well as the stamp issued by Venezuela, shown near the bottom of this webpage.

W. Mark Whitten, Norris H. Williams, and Mark W. Chase (2000) "Subtribal and generic relationships of Maxillarieae (Orchidaceae) with emphasis on Stanhopeinae: combined molecular evidence," in: American Journal of Botany 87: 1842-1856.
This article distinguishes the two groups of plants attributed to Houlletia at that time: "Euhoulletia," the red spotted group of species with triangular epichiles and "Neohoulletia," the pale yellow to white flowered species with rectangular or ovate epichiles, which Luckel & Fessel had moved into the new genus Jennyella a year earlier (1999).
Available
online.